1. Field of the Invention
The present invention relates to a ceramic matrix composite material, the matrix of which primarily consists of silicon carbide, and a manufacturing method thereof.
2. Description of the Related Art
Since silicon carbide (SIC) sinters are hard and resist abrasion, heat, oxidation, and alkaline well, many attempts have been made to apply the materials to slide members, turbine blades, reaction tubes, or sensor boxes used under severe conditions.
However, ceramic materials consisting of silicon carbide sinters are brittle; they are typically destroyed catastrophically under a tensile stress. It is strongly sought to increase the toughness and reliability of these materials in order to improve the reliability of SiC ceramic parts. Much research is being carried out on ceramic matrix composite materials where SiC ceramics are used as matrices in which continuous fibres, short fibres or whiskers of ceramics are compounded and dispersed.
An example of a conventional method of producing a ceramic matrix composite material is described herein. Short fibres or whiskers of ceramics are mixed with SiC powder to be used as a matrix, or a preformed compact made of continuous ceramic fibres is filled with SiC powder to create a compact including reinforcements. As is the usual way to manufacture sintered masses, either normal sintering, gas pressurized sintering, hot pressing, or hot isostatic pressing is used to sinter the shaped compact including reinforcements. Among these sintering methods, hot pressing and hot isostatic pressing are commonly used because normal sintering and gas pressurized sintering fail to provide dense sinter when a lot of reinforcement is added.
Sintering by hot pressing and hot isostatic pressing, however, has the degradation problem with reinforcements at high temperature and high pressure. Moreover, in the hot pressing method, part's shapes are to be simple.
Meanwhile, attempts are being made to use reaction sintered SiC as a matrix for ceramic based composite material. In reaction sintering, the dimension change due to sintering occurring less, a dense compact can be manufactured at a comparatively low temperature and low pressure which enables a large amount of reinforcement to be compounded in. On the other hand, conventional reaction sintering cannot fully prevent free metal (metal silicon) from remaining in the matrix. Sections occupied by free metals work in the same way as pores do at high temperature. The ceramic based composite material using a matrix of reaction sintered SiC, therefore, has a problem with strength at high temperatures.
Moreover, methods using synthetic organic precursors or chemical vapor infiltration (CVI) to form a matrix made of SiC are being tested. However, because a matrix manufactured with synthetic organic precursors has an amorphous structure containing much oxygen, the strength of the compact drops at high temperature. The CVI method also has other problems, among them the density of the manufactured compact being rather low and manufacturing and equipment costs high.
As stated above, conventional ceramic matrix composite materials using matrices of SiC have several problems including deterioration in reinforcement, limited part's shapes, and density of the sinter.
Thus a strong demand exists for the technology to produce a dense matrix which fully utilizes the characteristics of a SiC matrix benefiting from the effects of fibres, whiskers and other forms of ceramics, which allows a composite of comparatively large amounts of reinforcement and prevents the deterioration of reinforcements.